[Novalug] ext3 and noatime

[Mark Smith]

On Sun, Feb 03, 2008 at 11:31:00AM -0500, Richard Rognlie wrote:
> >  I'm researching on how to tune ext3 filesystems in Virtual machines 
> > using iSCSI. I have checked the performance of the raw disk is good 
> > (around 90-100 MB/s) but the performance of the underlying filesystem is 
> > low (around 16 MB/s).
> > 
> >  This guy claims that mounting the filesystem with noatime improves the 
> > performance:
> > 
> >  http://ubuntuforums.org/showthread.php?t=107856
> > 
> >  I've checked it together with nodiratime and writes boosted to 85 MB/s 
> > which is pretty similar to the raw disk performance.
> > 
> >  The guy in blog says that could lead to some problems using make but 
> > he hasn't experienced anything similar, does anyone know if this noatime 
> > settings could cause any data corruption or any problem? We are going to 
> > use it probably for Subversion repositories and maybe Apache websites.
> 
> noatime should not impact make and similar utilities, since they only
> really care about "mtime" not "atime".  I know of no utilities that 
> rely on atime for anything useful.  Any useful caching utilities
> might, but for the most part, you'd be using the cache itself for read
> not the underlying disk.

i'm pretty sure the tmp cleaner uses atime.  it'll only remove files that
have not been accessed in a while.  i can't think of anything else off the
top of my head though.

it's not shocking that removing atime updates improves performance.  any
time you avoid a write it's a performance win.

-- 
Mark Smith
mark at winksmith.com
mark at tux.org